- draw circle for example with radius 2 at crossing
- use the "break out segment" tool to delete the two segments you don't want (inside the circle)
- Delete half of circle, leaving something that looks like one wire jumped over the other one.
Alternately (and easier I think):
adopt the convention that crossing lines do not intersect unless there is a dot or small circle on the intersection. Then, you only need to paste a dot at each intersection, which is only 1 step.
I am running Ubuntu 8.04 GNU/Linux (Hardy Heron)